hey i just had that problem on my 92 scort, it would idle real lowat stoplights. i tried everything, than i noticed that there was a small crack in my intake tube that goes to the throttle body. The crack was on the bottom so i couldn´t see it right away. A small crack in it will make it run like crap when idling. check your intake hose for cracks. I just had the same problem your having to a tee, and i found i had a crack in it so i put some duct tape around it for temporary till i got a new hose. you should see an instant improvement when you close up the crack. let us know if what you find out, hope thats all it is